Stochastic orientational relaxation of a plastic crystal

Dielectric properties of cyanoadamantane in the plastic phase are studied u sing a stochastic model for orientational relaxation. The jump rate distrib ution is assumed to be a power law function, and the master equation is sol ved within the coherent medium approximation. The orientational relaxation function is shown to be fitted well by a stretched exponential function. Th e exponent of the power law distribution function is related to temperature by comparing the Cole-Cole plot of the complex dielectric constant with ex periments. The glass transition temperature is shown to correspond to the V ogel-Fulcher temperature where the relaxation time diverges.